Denial of Service Vulnerability in Rustls Library
Published Apr 19, 2024 · Updated Nov 3, 2026
Original summary
Normalized public record · Updated Nov 3, 2026
Denial of Service Vulnerability in Rustls Library
Publisher and source text is retained separately from QFinch interpretation.
QFinch assessment
rustls::ConnectionCommon::completeio could fall into an infinite loop based on network input.
Potential impact
This is a DOS. A multithread non-async server that uses rustls could be attacked by getting few requests like above (each request could cause one thread to spin) and stop handling normal requests.
Technical context
Verified at 0.22 and 0.23 rustls, but 0.21 and 0.20 release lines are also affected. tokio-rustls and rustls-ffi do not call completeio and are not affected. rustls::Stream and rustls::StreamOwned types use completeio and are affected. When using a blocking rustls server, if a client send a closenotify message immediately after clienthello, the server's completeio will get in an infinite loop where: - eof: false - untilhandshaked: true - self.ishandshaking(): true - self.wantswrite(): false - self.wantsread(): false
Evidence: public source recordsAffected products
| Affected package, product or range | Fix status |
|---|---|
| Consult the referenced vendor advisory for affected versions. | Consult source advisory |
Matching a version is only one part of assessing exposure. QFinch has not assessed your environment on this public page.
Remediation
Apply the vendor-supported fixed release or mitigation, then verify the affected component is no longer reachable.
- Confirm the affected product and reachable code path exist in your environment.
- Apply the vendor-supported patch or mitigation from the primary advisory.
- Rescan the exact deployed revision and retain verification evidence.
Evidence coverage
- SSVC priority
- MEDIUM
- Confidence
- Not available
- Aliases
- None reported
Scores appear only when corresponding evidence exists. Missing data is never interpreted as zero risk.
Sources and record history
Record history
Published Apr 19, 2024 · Last refreshed Nov 3, 2026